1. Field of the Invention (Technical Field)
The present invention relates to fiber optic switches, particularly the use of electro- or magneto-active materials to cause optical fibers to undulate.
2. Background Art:
Present day optical fiber technologies are revolutionizing the telecommunications industry. Tremendous advances have been made in the field of telecommunications over the past decade. It has been estimated that this technology is capable of carrying tens of millions of conversations simultaneously on a single optical fiber. Optical fiber communication systems offer many advantages over systems that use copper wire or radio frequency links as a transmission medium. They include lower transmission losses, higher bandwidths, higher transmission rates, lower implementation costs, greater reliability and greater electrical isolation characteristics. It is clear that optical fiber communication will dominate the telecommunications industry in the very near future because of advantages such as these.
An important task in any fiber optics telecommunication system is routing the transmitted data to the proper destination from among many destinations possible. This task is accomplished by a variety of fiber optics switches. As the use of fiber optics has proliferated in telecommunication systems, replacing wire, different routing fiber optic switches have been developed. They generally consist of only a few or several fiber optics channels.
Fiber optic switching is an important component in any telecommunication system. These systems use switches to establish communication channels among two or more of their interfaces. An optical fiber switch is capable of optically connecting, or aligning, any one of a first group of optical fibers with any one of a second group of optical fibers, or vice versa, enabling an optical signal to propagate through the optical interface junction from one fiber to the other.
When two optical fibers are aligned end-to-end, light entering one fiber (the input or sending fiber) will continue into and through the second fiber (the output or receiving fiber) while the two adjacent ends, or faces, are aligned and close together. Fiber optic switches misalign or disjoin the adjacent ends of the fibers by moving one or both of the two ends. By moving, for example, the first fiber""s end to a new location, the signal, in this case light, can be redirected into another, third fiber, by aligning the first fiber""s end with an end of the third fiber.
Lateral separation of the two adjacent ends will result in loss of light between the two fibers so that a light absorber is provided beside the fiber which either moves into place as the receiving fiber moves away or stays in place as the sending fiber moves away. Space is provided for this motion. This effectively switches the signal off. The discontinuity between the fiber ends may be either perpendicular to the fiber axis or at some angle to the axis but the gap is minimal when the fibers are aligned. Fibers may be collected into a bundle, a fiber optic cable, with a structure set up at the active location to permit the required motion of a fiber end. A fiber bundle can be separated from a circular bundle or other shaped cross-section to a linear arrangement where the fibers are in a straight line at the switch but reformed into a bundle again at the device exit.
Optical fiber switches generally utilize fiber positioning means, alignment signal emitter means and computer control means. Normally, a fiber positioning means is provided near the end of one fiber to selectively point the end of that fiber in one fiber group toward the end of another fiber in the other fiber group to perform a switched optical transmission. Patents proposing to perform such switching actions in fiber optic telecommunication systems include: U.S. Pat. No. 5,024,497, to Jebens, entitled xe2x80x9cShape Memory Alloy Optical Fiber Switch,xe2x80x9d which discusses switching activated by a shape memory alloy wire in a transverse direction. U.S. Pat. No. 4,512,036, entitled xe2x80x9cPiezoelectric Apparatus for Positioning Optical Fibers,xe2x80x9d U.S. Pat. No. 4,543,663, entitled xe2x80x9cPiezoelectric Apparatus for Positioning Optical Fibers,xe2x80x9d U.S. Pat. No. 4,651,343, entitled xe2x80x9cPiezoelectric Apparatus for Positioning Optical Fibers,xe2x80x9d and U.S. Pat. No. 5,524,153, entitled xe2x80x9cOptical Fiber Switching System and Method Using Same,xe2x80x9d all to Laor, use piezoelectric bimorphs for positioning optical fiber switches. U.S. Pat. No. 4,303,302, to Ramsey, et al., entitled xe2x80x9cPiezoelectric Optical Switchxe2x80x9d discusses other forms of piezoelectric bimorphs for optical fiber switching.
Patents discussing fiber optic switching include: U.S. Pat. No. 5,812,711, to Glass, et al., entitled xe2x80x9cMagnetostrictively Tunable Optical Fiber Gratings;xe2x80x9d U.S. Pat. No. 5,812,711 to Malcolm, et al., entitled xe2x80x9cMagnetostrictive Tunable Optical-Fiber Gratings;xe2x80x9d U.S. Pat. No. 4,759,597, to Lamonde, entitled xe2x80x9cMechanical Switch for Optical Fibers;xe2x80x9d U.S. Pat. No. 4,415,228, to Stanley, entitled xe2x80x9cOptical Fiber Switch Apparatus;xe2x80x9d U.S. Pat. No. 5,004,318, to Ohashi, entitled xe2x80x9cSmall Optical Fiber Switch;xe2x80x9d U.S. Pat. No. 4,844,577, to Ninnis, et al, entitled xe2x80x9cBimorph Electro Optic Light Modulator;xe2x80x9d U.S. Pat. No. 4,512,627, to Archer, et al., entitled xe2x80x9cOptical Fiber Switch, Electromagnetic Actuating Apparatus with Permanent Magnet Latch Control;xe2x80x9d U.S. Pat. No. 5,699,463, to Yang, et al., entitled xe2x80x9cMechanical Fiber Optic Switch;xe2x80x9d U.S. Pat. No. 5,841,912, to Mueller-Fiedler, entitled xe2x80x9cOptical Switching Device;xe2x80x9d U.S. Pat. No. 5,647,033, to Laughlin entitled xe2x80x9cApparatus for Switching Optical Signals and Method of Operation;xe2x80x9d U.S. Pat. No. 4,886,335, to Yanagawa, et al., entitled xe2x80x9cOptical Fiber Switch System;xe2x80x9d and U.S. Pat. No. 4,223,978, to Kummer, et al., entitled xe2x80x9cMechanical Optical Fiber Switching Device.xe2x80x9d These patents disclose various methods for fiber optic switching, including mechanical devices such as rods, motors, and adapters, as well as wave guides and reflectors. The Ohashi, Ramsey, Ninnis, Stanley, Jebens, Glass, and Laor patents disclose various methods and apparatuses that use piezoelectrics, magneto-strictive materials, and shape memory alloys, for bending the fiber; however, these patents are either complicated in their configurations or require additional mechanical means beyond these materials.
Other issued patents that disclose types of fiber optic switches include U.S. Pat. No. 5,915,063 to Colbourne, et al., entitled xe2x80x9cVariable Optical Attenuatorxe2x80x9d which discloses the use of a mirror that tilts in response to movement of a piezoelectric member, or magnetostrictive or eletrostrictive elements. The signal leaves one of the fibers and reflects off of the mirror which directs the signal into the other fiber depending on the tilt of the mirror. U.S. Pat. No. 5,808,472 to Hayes, entitled xe2x80x9cApparatus and Methods for Positioning Optical Fibers and Other Resilient Membersxe2x80x9d discloses positioning the free end of an optical fiber in the electric field of several electrodes and applying voltage to a conductive sleeve around the fiber which then responds to the electric field produced by the electrodes. U.S. Pat. No. 4,580,292 to Laor, entitled xe2x80x9cCommunications Exchangexe2x80x9d discloses the use of a bender element like the bender element disclosed in the above identified Laor patents, that is actuated by piezoelectrics. The free end of the optical fiber is attached to the bender element so that it can be moved by the bender element.
U.S. Pat. No. 5,870,518 to Haake, et al., entitled xe2x80x9cMicroactuator for Precisely Aligning an Optical Fiber and an Associated Fabrication Methodxe2x80x9d positions actuators in a complicated substrate apparatus for controlling the movement of an optical fiber. U.S. Pat. No. 5,216,729 to Berger, et al., entitled xe2x80x9cActive Alignment System for Laser to Fiber Couplingxe2x80x9d uses piezoelectric elements to control mirrors which direct a laser beam into an optical fiber, and piezoelectric transducers made up of vertical and horizontal elements that move in response to an applied voltage and thereby move the fiber. U.S. U.S Pat. No. 5,214,727 to Carr, et al., entitled xe2x80x9cElectrostatic Microactuatorxe2x80x9d discloses a microactuator for moving an optical fiber into alignment with one of several optical fibers by means of upper and lower substrates and a series of electrodes on the substrates which provide upper and lower torque stators. The fiber is moved by a conductive armature that responds to energy from the electrodes. U.S. Pat. No. 4,652,081 to Fatatry, entitled xe2x80x9cOptical Multi-Fibre Switchxe2x80x9d discloses coating a magnetic material on a fiber that causes the fiber to move in response to an energized solenoid around the fiber. U.S. Pat. No. 4,223,978 to Kummer, et al., entitled xe2x80x9cMechanical Optical Fiber Switching Devicexe2x80x9d discloses a mechanical switch for aligning and misaligning optical fibers.
As fiber optics telecommunication increases in application, the number of channels required for switching systems will multiply greatly. A switch that can accommodate dozens or even hundreds of channels will be valuable and effective. Designs based upon combinations of numerous small, movable mirrors and lenses to direct light from individual fixed fibers have been under development for some years by such organizations as Nortel Networks, and Lucent Technologies.
The present invention overcomes deficiencies in the prior art and simplifies optical switching by largely eliminating the mechanical structure necessary to move the fibers. The present invention provides movement of fiber optic channels by directly adhering an electro- or magneto-active material to the optical fiber itself, longitudinally to cause the fiber to undulate to the desired xe2x80x9c2xc2xd-Dxe2x80x9d position. The fiber moves by application of an electrical signal directly to the electro- or magneto-active material upon the fiber. The designation xe2x80x9c2xc2xd-Dxe2x80x9d used herein signifies that the displacement of the fiber may be both laterally and longitudinally. The present invention, being based on modifications of the inventions in the parent applications, allows input and output fibers to undulate in 2xc2xddimensions and accommodates a large number of optical channels without the use of complicated apparatuses or multiple movable mirrors.
The present invention is an optical switch wherein an activation material is adhered on individual optical channels so that when an electrical signal is applied to the activation material, the activation material contracts or expands and moves the optical channel accordingly. The activation material can consist of either an magneto-strictive material, a piezoelectric material, a piezoceramic material, a piezo-polymeric material, a shape-memory alloy material, or an artificial muscle material. The activation material is adhered longitudinally upon the free end of the optical channels in the form of activation strips or in the form of a jacket. Alternatively, three or four piezoelectric bimorph activation elements may be adhered to individual fibers so as to cause undulation motion in the various directions required. The electrical signal that is applied to the activation material can vary in amplitude, frequency or polarity in order to control the direction and amount of movement of the optical channel, as well as the frequency of its movement.
The activation strips or jacket of activation material is placed on either or both of the input and output optical channels. In this manner, either or both the input and the output optical channels to be aligned can move toward one another so that the emitted signal from the input optical channel is transmitted into the receiving face of the selected output optical channel upon activation of the activation material. Collimating lenses are provided on either or both of the input and output optical channels sending and receiving faces to focus the emitted signal into the selected output channel.
In the situation where the input and output optical channels are not arranged in an end-to-end fashion, a fixed mirror is used to reflect the emitted signal from the input channels toward the output channels. Additionally, the present invention includes a support frame for the input channels and a support frame for the output channels. The support frame defines a plurality of openings for each individual optical channel to fit through so that the optical channel is held stable while allowing the free end to undulate. The support frame is located just behind the activation material of each optical channel so that the optical channels are stabilized while still allowing the free ends to undulate. Each opening in the frame is designed in a shape allowing the individual optical channels to move freely in the directions necessary to send and receive the transmitted signal.
A primary object of the present invention is to provide an efficient and versatile means for optical switching by undulating the free ends of both the input and output optical fibers such that the selected input and output fiber move toward one another and the signal is directed from the input fiber into the selected output fiber.
Another object of the present invention is to undulate an optical fiber by placing electro-magneto-active material strips longitudinally along the optical fiber in order to move the optical fiber in 2xc2xd dimensions in response to an electrical signal applied to the strips.
A primary advantage of the present invention is that the fibers move in response to the electrical signals applied to the electro- or magneto-active materials adhered directly to each fiber, and does not require additional mechanical means to move the fiber.
Still another advantage of the present invention is that each input and output optical fiber can be moved in 2xc2xd dimensions thereby increasing the versatility of the optical switch.
Other potential advantages provided by the present invention, due to its simplicity and design, are long life, reliability, low cost, and a variety of applications.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.